Nozzle for foaming, spraying or misting
1. Field of the Invention
The invention relates to a nozzle for foaming, spraying or misting a free-flowing medium.
2. Prior Art
It is known that foamed concrete in the construction industry is produced from the foaming materials in a special foaming stirrer. Instead of the foaming stirrer it is also known to use a free-fall mixer. A further method dispenses with foaming agents; the concrete mixture is in this case loosened in a drum provided with tines, pins or teeth. There is also the possibility of producing foamed concrete by pressing air in a free-fall mixing drum.
In the methods outlined, the foam is already produced directly in the storage container area and then has to be conveyed over a relatively long path to the point of use. However, on the path to the point of use there is the risk that the foam will collapse as a result of different effects or merely because of the transport duration per se. For example, the mixer can get into a traffic jam or different external temperatures act on the mixer, so that different conditions are encountered in the area of the “concrete pump”. Accordingly, it is not possible at all to predict what foam will arrive at the point of use after a certain conveying path or conveying height. For example, the finished foam mixture has to cover an awkward and long transport path in order to be used in a rough area, for example on the tops of mountains. Accordingly, it is not possible to set the quality and therefore the dry or set bulk density of the foam material reproducibly.
Although it is known always to produce approximately the same foam with the aid of spray containers, such as spray cans or fire extinguishers, this is only possible as long as the respective container is filled with the liquid medium and the propellant. In the case of a greater requirement for foam, such as in the construction industry, the use of such containers is not suitable. In addition, the foaming method cannot be set variably by means of such containers.
DE 195 37 239 C2 reveals a foaming nozzle which has an inlet for the medium to be foamed and an inlet for gas. Also provided is an annular gap and a flow connection between the annular gap and the main flow duct. Furthermore, an outlet is provided for the foam produced within the foaming nozzle, said outlet being located opposite the inlet for the liquid.
Furthermore, U.S. Pat. No. 4,830,790 discloses a foam producing nozzle which, in addition to an inlet and an outlet, is provided with elements that generate turbulence. The apparatus has an inlet opening and an outlet opening Provided in the central area of the nozzle arrangement, as an element that generates turbulence, is a baffle plate provided with openings, downstream of which air intake openings are connected.
In addition, DE-A 38 41 123 A1 discloses a nozzle mixing element for the dry spraying of concrete in the form of a pipe connector, in which bores pointing radially inward are provided in the inner area as injection elements.
Finally, WO 82/01141 reveals a foaming nozzle which has an inlet opening for the introduction of water under pressure and an inlet opening for the introduction, for example, of a liquid detergent. The liquids pass into a main flow chamber at whose end a nozzle is arranged. An outlet opening follows the nozzle. In the area of the nozzle there is an axially displaceable, pin-like nozzle core, which can be displaced both into an active foaming position and, in this position, rests substantially in the nozzle. If the nozzle core is withdrawn axially from the nozzle, it is located in a passive position, which permits a free flow of the liquid produced through the nozzle to the outlet duct.